In order to overcome the limitation of conventional cleaning method by workers, variety attempts to develop a window cleaning apparatus has been tried. However, the existing cleaning devices were lack of consideration for avoiding projection parts of the window such as frames or profiles. In this study, operating mechanism of cleaning tool for avoiding the projections parts using a two-axis robot is proposed. Proposed mechanism is that a wiper are reposed in a relatively stationary in the vicinity of the projection and avoided the projection in this state. It is expected that the mechanism is the base of driving cleaning tool part in the new window cleaning apparatus.